Following the constant progress in different technological fields, people living in the modern society require more and more information to satisfy the need in their work, daily life, and entertainment. Therefore, for many people, a mobile communication device capable of providing various kinds of real-time information has become a requisite for life. Meanwhile, all the mobile communication device manufacturers also engage themselves in improving or increasing the functions of various types of mobile communication devices to satisfy the demands of different types of users.
The arrangement of the keypad on the mobile communication devices has a great influence on the users' habit in operating the devices, particularly when the users frequently use the mobile communication devices to send and receive short messages. Generally, a conventional mobile communication device has a keypad located below a display screen. A user would usually stably hold the device with two hands, in order to input text by pushing the keys on the keypad. Since most of the mobile communication devices have a center of gravity located at the display screen and a very small keypad size, it is difficult for users to stably hold the mobile communication devices with only one hand. Further, when a user holds a mobile communication device with only one hand and uses the thumb of the same hand to push the keys on the keypad, it would be uneasy for the thumb to push the keys located closer to the hand, resulting in a slowed input speed or incorrect input via wrong keys. Since the other four fingers of the same hand are used to hold the mobile communication device at one side opposite to the thumb, they are not effectively used to operate the keys. Moreover, with the display screen located above the keypad, someone else around the user can easily peep the text input by the user and shown on the display screen, resulting in undesired disclosure of personal privacy.